The min timestamps vary (likely due to read repairing old values into the memtable and flushing into these sstables), but the max timestamps for both are in the same second (same microsecond, even, so probably the same write):

Maximum timestamp: 1544903882074190

Maximum timestamp: 1544903882074190

jjirsa:~ jjirsa$ date -r 1544903882

Sat Dec 15 11:58:02 PST 2018

TWCS buckets based on max timestamp per file, so they belong together:

so this the situation before - 3 nodes in the cluster (3.11.3 in this case but i saw same thing in 2.1 and 3.0), there is a script writing one row every minute and another script doing nodetool flush every 10 minute.window is defined as two hours, so after a few days this is how the directory listing looks :

check out sstable 873 is from dec 15. at this point i remove node no 3.

and the log shows streamed data is creating sstables 1150-1200. it also shows one of these sstables being compacted with sstable 873, resulting in sstable number 1228, an operation which from what i understand should not happen.

After removing a node from the cluster, a table that is defined as TWCS, has sstables from different time windows merged together, making old and new data sit in the same sstable(the full example is in the ticket).